This fixes "hg qimport -r null". Previous versions used to:
- Traceback because null revision mutability was not defined
- Add an empty -1.diff patch to the series
The error message:
abort: revision -1 is not mutable
is symptomatic of a deeper problem in phase command revision handling. It could
be fixed easily in the command itself but I feel a better fix must be done in
phase API which raises the issue of phase updates atomicity: aborting in
phases.advanceboundary/retractboundary requires a better rollback behaviour to
avoid partial changes.
When trying to import a url that ends with a slash
os.path.basename() would return an empty string. So
when seeing a leading slash, remove it and infer the
patch name from the remaining url.
e.g. `hg qimport http://paste.pocoo.org/raw/xxx/`
deduced '.' to be the patch name. Now we'll deduce 'xxx'.
